JPS6049316A - Liquid-crystal shutter device - Google Patents

Abstract

PURPOSE:To increase the degree of light shielding, to maintain a response speed, and to improve a contrast ratio by adding coloring matter which absorbs light in a wavelength range of high transmittivity selectively to nematic liquid crystal. CONSTITUTION:Transparent electrodes are formed on the internal surfaces of glass substrates 2 and 4, a rubbing orientation treatment is performed, and nematic liquid crystal 6 incorporating the coloring matter is sealed between both surfaces encircled with sealing materials 3 and 3. Then, polarizing plates 1 and 5 in a parallel Nicol state are arranged outside of this liquid-crystal device. Liquid-crystal molecules are directed at right angles to each other on the rubbing-treated surfaces. The coloring matter uses, for example, blue anthraquinone coloring matter and is added to the nematic liquid crystal 6 by 1.5wt%. Consequently, even when the cell thickness is held constant without being increased, the degree of light shielding is increased, and the contrast ratio is improved while the response speed is unchanged.

Description

[Detailed description of the invention] Technical fields> The present invention relates to a liquid crystal shutter for a liquid crystal display device.

Problems to be Solved> Recently, the use of liquid crystal shutters as printer heads has been attracting attention as a way to expand the use of liquid crystal display devices. What is required when using this liquid crystal shutter is both a high contrast ratio and high-speed response characteristics. However, when using a TN-FEM LCD, which is currently widely used in liquid crystal display devices, as the liquid crystal shutter, there is a limit to the simultaneous achievement of a high contrast ratio and high-speed response characteristics. For example, in a negative LCD, the contrast ratio is determined by the transmittance when no voltage is applied. In addition, this negative type LCD has a property that the higher the degree of light shielding, the higher the contrast ratio. What determines the contrast ratio and the transmittance when no voltage is applied is the product ΔnXd of the refractive index anisotropy Δn of the liquid crystal material and the thickness d of the liquid crystal layer.

The degree of shielding of the culm base with a large value of ΔnXd increases.

Therefore, possible ways to increase the degree of shielding of light include using a liquid crystal material with a large value of Δn, or increasing the thickness of the liquid crystal material, that is, the cell thickness d.

However, all of the above methods have the disadvantage of slowing down the response speed.The factors pointed out to this are that the viscosity of the liquid crystal material and the cell thickness determine the response speed, especially the fall time in this case. In other words, increasing the cell thickness increases the degree of light shielding, but at the same time slows down the response speed.On the other hand,
Although it is possible to use a liquid crystal material with a large Δn,
Known liquid crystal materials have relatively high viscosity, which also results in slow response times. Furthermore, even if the response speed is sacrificed to some extent, the size of Δn is 0.26 or more for known liquid crystal materials.
．． Limited to approximations in the range of 28 or less. Therefore, in order to meet the requirements for a contrast ratio higher than that achieved with this value, there was no other option than to increase the cell thickness.

<Object of the Invention> The present invention has been made in view of the above-mentioned conventional drawbacks, and an object of the present invention is to provide a liquid crystal shutter device that can increase the contrast ratio without reducing the response speed.

<Configuration of the Invention> The liquid crystal shank device of the present invention is characterized in that a dye that selectively absorbs light in a wavelength region with relatively high transmittance is added to a nematic liquid crystal.

<Example> The present invention will be explained in detail below.

FIG. 1 shows a liquid crystal shutter device. A transparent electrode is formed on the inner surface of the glass substrate 2.4, which is subjected to a rubbing alignment treatment, and a nematic liquid crystal 6 to which the dye of the present invention is added is sealed inside the glass substrate 2.4 surrounded by sealants 3, 3. There is.

On the outside of this liquid crystal device is a polarizing plate 1 in a parallel Nicol state.
．． 5 is placed. The directions of the liquid crystal molecules on the rubbed surface are perpendicular to each other.

The nematic liquid crystal 6 is a biphenyl-pyridine liquid crystal (ROTN-403 manufactured by Rossosh, Δn=0
．． 26. Viscosity 66C, P,
11, maximum absorption wavelength of 660 nm) was selected and added to the nematic liquid crystal 6 in an amount of 1.5% by weight.

FIG. 2 is a graph comparing the transmittance before the addition of the dye (no dye) and after the addition (with the dye) when four applied voltages are turned off. Although the cell thickness d is shown as 7.7 μm, it can be seen that on the wavelength side longer than wavelength λ-600 nm, the transmittance after addition is significantly lower than that before addition. The contrast ratio at this time was 67 without the dye, but increased to 86 with the dye.

Regarding the response speed, the rise time is 1.4ms when the applied voltage is 20V, and the fall time when it is off is 45m5.
Therefore, there was almost no change even when the above dye was added. Therefore, even when the cell thickness is kept constant without increasing it, it is possible to increase the degree of light shielding, and it has become possible to increase the contrast ratio without any change in response speed.

<Effects of the Invention> As explained above, according to the present invention, by adding a predetermined amount of a dye that selectively absorbs light in a wavelength region with high transmittance to a nematic liquid crystal, the degree of shielding of light is increased.
It was possible to increase the contrast ratio without reducing the response speed.

[Brief explanation of drawings]

FIG. 1 is a diagram exemplary showing the configuration of a liquid crystal shank device of a TN-FEM, and FIG. 2 is a characteristic diagram showing the effects of the embodiment of the present invention. 1.5-Polarizing plate 2.4-Glass substrate 3-Sealing material 6-Nemateisoku liquid crystal patent applicant Sharp Corporation agent Patent attorney Arata Nishida

Claims (1)

[Claims] A liquid crystal shutter device that uses a twisted nematic field effect mode liquid crystal display device as a shutter, characterized in that a dye that selectively absorbs light in a wavelength region with relatively high transmittance is added to the nematic liquid crystal.